Windows provide natural light, fresh air, access, and connection to the outside world. However, they also represent a significant source of wasted energy. With the growing trend in increasing the use of architectural windows, balancing the conflicting interests of energy efficiency and human comfort is becoming more and more important. Furthermore, the concerns with global warming and carbon foot-prints are adding to the impetus for novel energy efficient glazing systems.
In this regard, windows are unique elements in most buildings in that they have the ability to “supply” energy to the building in the form of winter solar gain and daylight year around. In current applications, they are responsible for about 5% of the entire U.S. energy consumption, or about 12% of all energy used in buildings. Current window technology often leads to excessive heating costs in winter, excessive cooling in summer, and often fails to capture the benefits of daylight, that would allow lights to be dimmed or turned off in much of the nation's commercial stock. These factors result in an energy “cost” of over 5 Quads: 2.7 Quads of energy use annually in homes, about 1.5 Quads in the commercial sector, and another 1 Quad of potential lighting energy savings with daylight strategies. Advances have been made over the last two decades primarily in reducing the U-value of windows through the use of static low-E coatings, and by reducing the solar heat gain coefficient, SHGC, via the use of spectrally selective low e coatings. However, further enhancements are still possible.
With the ability to dynamically control solar heat gain, loss, and glare without blocking the view, electrochromic windows (ECWs) may provide a significant reduction in energy use. Indeed, ECWs have the potential to impact all the window energy end uses, e.g., by reducing cooling loads in climates where windows contribute to substantial cooling loads while allowing the same window to admit solar gain in winter to reduce heating, and modulating daylight to allow electric lighting to be reduced in commercial buildings while also controlling glare. For example, as the exterior light and heat levels change, the performance of the window can be automatically adjusted to suit conditions via an automated feedback control.
Electrochromic (EC) windows are known. See, for example, U.S. Pat. Nos. 7,547,658; 7,545,551; 7,525,714; 7,511,872; 7,450,294; 7,411,716; 7,375,871; and 7,190,506, the disclosure of each of which is incorporated herein by reference.
Some current EC dynamic windows provide transmissions ranging from about 3% in the tinted state to about 70% in the clear state. As indicated above, the solar heat gain control (SHGC) range is quite large. Indeed, some current EC dynamic windows provide an SHGC range from about 0.09 in the tinted to about 0.48 in the clear state. Lithium based-inorganic EC technology also offers the advantages of durability, low voltage (less than about 5V) operation, clarity (70%), transparency when power is off, and low energy consumption. Despite these broad ranges, current lithium-based inorganic ECWs unfortunately offer limited color variation, and maximum opacity could be improved (e.g., relative to other switchable glazing types). Another drawback with current lithium-based inorganic ECWs relates to their slow switching times. Indeed, current switching times for lithium-based inorganic ECWs typically range from about 5-10 minutes. Proton-based inorganic and organic polymer device mechanisms switch somewhat faster (e.g., 15 seconds to 5 minutes) but unfortunately suffer from degradation of the ionic conductor in the former case and degradation of the polymer in the latter case. The operational voltage for lithium based inorganic as well as proton-based inorganic and organic polymer type EC devices typically operate with 1-5 V DC and typically consume 2-3 W/m2 when switching and 0.5-1 W/m2 while maintaining the tinted state.
FIG. 1(a) is a schematic diagram of a typical electrochromic window, and FIG. 1(b) is a schematic diagram of a typical electrochromic window in a tinted or colored state. The active stack 100 shown in FIG. 1(a) includes four components, namely, first and second transparent current collectors 102 and 104; a cathode 106 (and often the coloration layer); an electrolyte 108 (which is ionically conducting but electrically insulating); and an anode 110, which is the source of the active ions (e.g. Li, Na, H, etc.) that switch the glazing properties upon transfer to and from cathode. The anode 110 may be a coloration layer, if coloration occurs anodically, e.g., as ions exit the layer. These components are sandwiched between first and second glass substrates 112 and 114. Fundamentally, the electrochromic device dynamically changes optical absorptivity, with the movement (intercalation and de-intercalation) of the Li into and out of the cathode 106. This, in turn, modulates the interaction with solar radiation thereby modulating the SHGC for energy control, as well as visibility and glare (important for human comfort). Because Li is in the cathode 106, the electrochromic window in a tinted or colored state and only a portion of incident light and heat are transmitted through the ECW.
Unfortunately, current ECW films do not meet the required performance in appearance (including color), switching speed, quality consistency, and long term reliability. Adequate supply and useful window sizes are additional issues.
One reason the current high ECW cost structure is above the market threshold is that the EC device fabrication is incompatible the fabrication flow of the glazing industry. One critical safety requirement in the building code is that the outermost glass in an insulated glass unit (IGU) be tempered. Also, according to practice in the coated glass industry, large sheets of glass (typically up to 3.2 m wide) are first coated, then sized, and finally tempered. In an ideal situation, the EC finished glass could be tempered and cut to size. However, tempered glass cannot be cut. Accordingly the practice in the coated glass industry is that large sheets of glass (typically up to 3.2 m wide) are first coated and then sold to the window fabrication sites where they are sized and tempered. Unfortunately, tempered glass cannot be cut afterwards, and the EC glass cannot be tempered after EC fabrication because the tempering temperatures would destroy the EC device. Consequently, current ECW fabrication techniques rely on already cut and tempered glass for EC fabrication. This is problematic for several reasons. For example, incoming tempered glass has a wide variation in thickness leading to substantial variation in the properties of the coating. Additionally, the presence of multiple substrate sizes and types leads to challenges in process control, throughput, and yield, which makes reproducible high yielding high volume manufacturing difficult.
FIG. 2 is a block diagram illustrating a current ECW fabrication process. The outermost glass is cut to size and tempered in 202, which corresponds to an EC glass fabrication process. The EC device is fabricated, e.g., so that it has the layer structure shown in FIG. 1(a), in 204. After the EC layers have been deposited, the EC device is patterned in 206, e.g., to reduce defects and improve yield and appearance. Bus bars are added to provide “electrification” (e.g., wiring) for the EC device in 208. A second substrate is added in spaced apart relation to the EC device, e.g., as shown in FIGS. 1(a) and 1(b). Together, 204, 206, 208, and 210 represent an insulating glass (IG) unit fabrication process. This IG unit may ultimately be incorporated into an ECW, e.g., as shown on the left-hand side of FIG. 1(b).
Another impediment to progress has been the limited resources and capabilities of the manufacturers in developing deposition sources, platforms, and automation that are compatible with high-throughput large-scale manufacturing techniques.
The most practical place to have the EC coating is on the inner surface of the outermost lite. The placement of bus bars on this surface for electrification (e.g., wiring) presents challenges not only to current IG fabricators, but also to glazers. Architects, commercial building owners, and end-users require information about the durability of the EC window over long durations of time. The reliability of the IG unit seal therefore is a concern. The EC IG unit differs from conventional windows in that interconnections to power the device must pass through the moisture barrier seal. There are no standards for interconnects and feed-throughs that preserve the seal integrity. What is on the market is proprietary. There are also concerns about the durability of the EC film stack when exposed to the range of solar and environmental stresses that a window experiences over its lifetime.
Finally, the device performance in terms of appearance, color, switching speed, consistency, SHGC range, and lifetime needs consideration. For example, architects have a strong preference for a neutral colored window that switches from dark gray to perfectly clear. Most EC windows on the market today exhibit a dark blue hue when colored and a yellowish tinge in the clear state. A more neutral color and enhanced transmission in the clear state would broaden the accessible architectural market.
Thus, it will be appreciated that there is a need in the art for improved electrochromic dynamic windows, and/or methods of making the same. For example, it will be appreciated that there is a need in the art for (1) low cost, large scale, high throughput coating techniques that are compatible with high-volume manufacturing (HVM); (2) a better performing EC formulation; (3) a robust, high throughput, low defect EC formation for large-size lites; and/or (4) coupling such new manufacturing techniques with existing post-glass fabrication and the ancillary technologies for producing complete windows. These and/or other techniques may help solve some of the above-noted and/or other problems, while also providing for more complete building control integration.
Certain example embodiments relate to top-down and/or bottom-up changes to (a) materials, (b) the electrochromic device stack, (c) high volume compatible process integration schemes, and (d) high throughput, low cost deposition techniques and equipment. In so doing, certain example embodiments may be used to provide reduced cost EC assemblies, en route to “Net-Zero Energy Buildings.”
One aspect of certain example embodiments involves the incorporation of novel electrochromic materials. For example, certain example embodiments involve an optically doped cathode and/or anode for greater visible transmission in the clear state, greater solar heat gain control (SHGC) delta between these states, improved appearance, and better reliability. Controlling the stoichiometry of WOx (e.g., so that it is sub-stoichiometric) advantageously may result in improvements with respect to the SHGC delta and better appearance (e.g., in terms of coloration). Anodically coloring the counter electrode also may increase the SHGC delta.
Another aspect of certain example embodiments involves the incorporation of a novel electrochromic device stack. For example, the inclusion of a low-cost, low-Fe mid-lite substrate may help reduce the need for substrate-device barrier layers. An improved transparent current collector (TCC) with much higher conductivity and transmittance than ITO may be provided for increased switching speed and reduced cost. The inclusion of a lithium phosphorus oxynitride (LiPON) electrolyte material may be selected for reliability purposes in certain example embodiments. Additionally, the use of transparent dielectric/conductive layers may be used to shift the color based on selective interference in certain example embodiments.
Still another aspect of certain example embodiments involves novel techniques for electrochromic device integration. For example, certain example embodiments may involve the use of laminated/bonded glass for the outer lite of EC IG unit. This may advantageously result in the complete elimination of the use of tempered glass in EC fabrication step, reduce the need for glass sizing and tempering before EC processing, enable the use of a single standard type and sized glass in EC fabrication for best process reproducibility and economy of scale, and/or enable post-EC fabrication sizing of glass. It also may advantageously enable device patterning after all EC layers have been deposited, thereby reducing the likelihood of defects and improving yield and appearance.
Yet another aspect of certain example embodiments relates to HVM-compatible deposition source development. For example, a novel LiPON deposition source capable of achieving high deposition rates and modulating growth kinetics may, in turn, enable high throughput and better film characteristics in certain example embodiments. Certain example embodiments also may use a novel linear showerhead based Li evaporator with remote, normal ambient compatible Li sources.
In certain example embodiments, a method of making electrochromic windows is provided. A first glass substrate is provided. Electrochromic device layers are disposed on the first substrate, with such layers comprising at least counter electrode (CE), ion conductor (IC), and electrochromic (EC) layers. The electrochromic device layers are patterned, and the first glass substrate with the electrochromic device layers disposed thereon is cut so as to form a plurality of EC device substrates. A plurality of second glass substrates is provided. The plurality of EC device substrates is bonded or laminated to the plurality of second glass substrates, respectively. A plurality of third glass substrates is provided. A plurality of insulating glass (IG) units is formed, respectively comprising first and second substrates in substantially parallel, spaced apart relation to the third glass substrates.
In certain example embodiments, a method of making an electrochromic (EC) assembly is provided. First, second, and third glass substrates are provided, wherein the second substrate is thermally tempered and the first substrate is not thermally tempered. A plurality of EC device layers are sputtering-deposited, directly or indirectly, on the first substrate, with the plurality of EC device layers comprising a first transparent conductive coating (TCC), a counter electrode (CE) layer, ion conductor (IC) layer, an EC layer, and a second TCC. The first and second substrates are laminated or bonded to one another. The second and third substrates are provided in substantially parallel and spaced apart relation to one another. The CE and EC layers are both color changeable when the EC assembly is in operation.
In certain example embodiments, a method of making an electrochromic (EC) assembly is provided. A plurality of EC device layers are sputtering-deposited, directly or indirectly, on a first substrate, with the plurality of device layers comprising, in order moving away from the first substrate, a first transparent conductive coating (TCC), a cathode layer, an electrolyte layer, an anodically coloring anode layer, and a second TCC. The first substrate with the plurality of device layers sputter-deposited thereon is connected to a second substrate such that the first and second substrates are in substantially parallel and spaced apart relation to one another.
In certain example embodiments, an electrochromic (EC) assembly is provided. First, second, and third glass substrates are provided, with the second and third substrates being substantially parallel to and spaced apart from one another. A plurality of sputter deposited EC device layers are supported by the first substrate, with the plurality of EC device layers comprising a first transparent conductive coating (TCC), a counter electrode (CE) layer, ion conductor (IC) layer, an EC layer, and a second TCC. The first and second substrates are laminated or bonded to one another. The second substrate is thermally tempered and the first substrate is not thermally tempered.
In certain example embodiments, an electrochromic (EC) assembly is provided. At least first and second glass substrates are provided, with the first and second substrates being substantially parallel to and spaced apart from one another. A plurality of sputter deposited device layers are supported by the first substrate, with the plurality of EC device layers comprising a first transparent conductive coating (TCC), a doped and anodically coloring counter electrode (CE) layer, an ion conductor (IC) layer, a doped EC layer comprising WOx, and a second TCC.
In certain example embodiments, an electrochromic device including a plurality of thin-film layers supported by a first substrate is provided. The plurality of layers comprises a doped and anodically coloring anode layer; an electrolyte layer comprising Li; and a doped cathode layer comprising WOx.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.